Jump to content


Member Contributer
  • Posts

  • Joined

  • Last visited

  • Days Won


sfdownhill last won the day on May 31

sfdownhill had the most liked content!


About sfdownhill

  • Birthday 04/14/1964

Profile Information

  • Location
    Vista CA
  • In My Garage:
    2001 VFR
    2010 Aprilia RSV4 track bike
    2003 CRF450R

Recent Profile Visitors

5234 profile views

sfdownhill's Achievements

Rising Star

Rising Star (9/14)

  • Dedicated Rare
  • Reacting Well Rare
  • First Post
  • Posting Machine Rare
  • Collaborator

Recent Badges



  1. Thanks for that info Cogswell. And yikes - my headers don’t have bungs for the OEM O2 sensors. Plus they’re already ceramic coated. Dang. Well, it’s just another of those puzzles we solve when modding our VFRs.
  2. Glad to hear it, ae86andkp61. I’m with you on the RB vs PC - I’m considering going from my current PC3 to RB w MTB when I do velocity stack and airbox mods on my 5 gen. Yaman is the man at RB USA, and there are a number of members here that he’s helped with setting up AFR maps for their RB systems, so that’s a consideration. Cogswell, my understanding is that it’s not so critical to keep the OEM O2 sensors with RB if you’re running MTB. Without MTB, the OEM sensors send O2 sensor readings to RB, which then communicates with the ECU to manage fueling. MTB takes over those duties when installed. What I’m not certain about is whether it’s important to have the RB connected to the OEM O2 sensor connectors going to the wire harness/ECU if you’re running MTB, or if MTB negates the need for OEM O2 sensors altogether. It’s a good question for Yaman at RB USA; as mentioned above, he’s a great resource for assistance when setting up a RB system, with or without MTB.
  3. The only difference between the 5 gen headers and the 6 gen headers is the 6 gens have 5/8” cut off their collector exit pipe to allow the complex 6 gen midpipe/dual muffler assembly to fit. Having just installed a set of 6 gen mufflers on these headers, I’m thinking we should have cut off 3/4”...maybe even 7/8”. Any other 6 gen owners think a little bit shorter collector exit would have been a better fit?
  4. 114hp is what a good 5 gen puts out on a generous dyno with the following mods: -WiLD headers from VFRD -good slipon midpipe/muffler -K&N air filter -Power Commander -a good dyno tech that knows how to tune
  5. (Laughing) You probably only need to read the first 6 or 8 pages to get the gist.
  6. Thumbs up!! You MUST remove the PAIR system prior to tuning because the PAIR dumps fresh air into the exhaust gases. This causes both onboard O2 sensors and dyno O2 sensors to get an AFR reading that is far leaner than actual. The minimum order is 15. Actually there are a few others interested in the headers, so possibly 6 or 7 including DivisibleRex, but it’s not official that there is a list or another production run happening.
  7. There’s not a waiting list at this time, but we’re keeping track of interested parties and if it the numbers keep increasing, there might be the possibility of another batch.
  8. Nice to see VFR guys helping each other out. vfrcapn, you know this, but for others who may not, it’s the 1998-1999 headers that have larger diameter tubes and no catalytic converter. A fair number of VFR owners have replaced stock skinny-tubed catalytic converter headers on 2000-2009 models with success (they work on 6th gen too). The only downside to the 98-99 headers is that they are mild steel, not stainless.
  9. bit loud just off idle and low RPM, resonating in my helmet a bit but smooths out and much less noticeable after that Less noticeable after that because the decibels just get further and further behind you as you twist your right wrist - ha!
  10. The electrical diagram in the service manual shows that from the harness to the natural color O2 sensor connector is cylinders 1-2 (left rear - left front) From harness to black O2 sensor connector is cylinders 3-4 (right rear - right front)
  11. Are your stock cans hollowed out or ‘gutted’ as some describe it? The tubing inside OEM is crazy constrictive - it consists of multiple very small diameter tubes that reverse the direction of the exhaust gases, passing them back and forth inside the OEM cans. If you haven’t cut out all the plumbing inside the OEM cans and replaced it with straight-through perforated tubes (with packing around the perf tubes), there will be too much back pressure to take advantage of the headers’ performance. Below are some photos of what you see when you cut open OEM 6 gen mufflers. Gases come in through a single inlet pipe and are immediately pushed through a perforated metal plate that is perpendicular to gas travel (A giant flow clogger). Then the gases push through two tubes into the middle chamber, then gases that are too willful to meet Honda engineers’ expectations reverse course through other tubes to circulate at the front of the can, then reverse course again to mix again in the mid chamber with gases that have remained in the middle chamber. Finally it’s all pushed out through the two little exit pipes we are familiar with. Here’s the screen over the inlet pipe way down at the bottom of the can (after all other midsection crap has been removed): Here’s the skinny little inlet pipe after removing the screen: Here are the noodly back and forth tubes in the midsection - now we know why OEM 6 gen mufflers are SO quiet! (Note the perforated sound damping material lining the inner walls of the can): ShipFixer, I’d suggest running the Delk until you find an open flowing slipon assembly with aesthetics that please you. Back pressure is never good with quality headers. Some say back pressure is a necessary component of a tuned exhaust, but the way it was described to me is that the column of gas moving through the exhaust system (Specifically after the final merge/collector) needs to have as little obstruction as possible. In a single muffler system, sometimes a longer canister works better, not because of back pressure, but because the column of moving gas spends a longer time moving through a controlled path, which in some cases allows the timing of exhaust pulses in the merges to be optimized. An example of this is my Aprilia RSV4 - another V4 - on which I had dyno runs done back to back, first with a 300mm long Akrapovic can then with a 420mm long Akrapovic. The cans were identical in all dimensions but length, and the bike put out 1.2 more hp and 2.3ft/lbs more torque with slightly richer fueling on the longer muffler. YMMV.
  12. It’s been a couple years, but on the 8 gen test bike, the O2 sensor in the rear bung didn’t seem as tightly spaced as with your installation Cogswell. I like the 270° turn you put in the cable - that seems to allow a decent routing. Is the bike in the photo your Torocharged 6 gen? That would be a great candidate for the headers.
  13. I use a light application of anti-seize on the studs when installing the headers. ‘Light’ meaning just enough to cover the threads, then wipe off as much of the anti-seize as I can with a gloved finger. With this treatment, no nuts have come loose or frozen in place on our three test bikes in the ~ 2 years since we started this project. Granted, 2 years isn’t much compared to the 16-20 years that some header nuts have been subjected to road spray and contaminants, but I was able to easily remove the headers from my 5 gen recently.
  14. Sounds good Stray - glad it’s working out. You are correct about the front two cylinders’ pipes being a pain in the buttocks to fit. It turns out that the original Two Brothers headers we copied were bent...dang. At the time the fixtures were built for 5/6 gen in 2018, the last thing on our minds was cutting up one of the last known ‘magic TBR headers’ in captivity to correct their alignment.
  • Create New...

Important Information

By using this site, you agree to our Privacy Policy.